In current disk drive systems that employ flying heads, there is a protective film of air between the head and the disk, where no contact is intended to occur during head read/write operations. The read/write head is typically a part of or affixed to a larger body that flies over the disk and is typically referred to as a “slider.” The slider also includes a surface referred to as an air bearing surfaces (ABS). The ABS has aerodynamic effects such as compression or expansion of air to generate positive or sub-ambient pressure. The ABS may include a flat surface, step, cavity, and/or taper. The ABS may also be referred to as a rail in the industry. The slider's body is attached to a suspension arm via a head gimbal assembly that biases the slider body towards the disk. The net effect of the ABS and the suspension arm is to cause the slider and the affixed head to fly at the desired height when the disk is at full speed. The net effect also causes the slider to be in contact with the disk surface, when the disk is at rest, in a contact-start-stop (CSS) zone of a disk in CSS drive systems. The portion of the slider that contacts the disk's surface is typically the aforementioned one or more rails.
CSS drive systems dedicate a portion of the disk's surface, referred to as the CSS zone, for the slider to reside when the drive is not in operation. With this type of system, the slider directly contacts the disk's surface in the CSS zone. The CSS zone interaction between the slider and the disk's surface is of great concern in the reliability of a drive system since it can be the major initiator of failure in hard disk drives. In order to improve the CSS performance, it is well understood that friction must be minimized between the slider and the disk's surface. Static friction, or stiction, is a term used to describe the force exerted against the motion of the slider relative to the disk surface when the slider is at rest on the disk surface. Stiction can be strong enough to prevent the drive motor from turning, or worse yet, can damage the slider by causing the slider to become detached from the suspension assembly or by causing the slider to damage the disk surface during separation of the slider from the disk surface.
One solution intended to reduce stiction when slider contacts occur in contact-start-stop (CSS) drives involves laser texturing of the CSS zone. In laser texturing, a laser beam is focused to a small spot on the disk surface, forming uniformly shaped and sized features, called “laser bumps,” in a controllable pattern. The laser bumps reduce the area of contact with the slider, thereby reducing the stiction behavior of the slider and disk surface interface. Although such a solution may reduce the stiction between the slider and disk surface in CSS drives, the laser texturing of a disk's surface is one of the more expensive steps in the manufacturing of magnetic recording disks. The continuing trend to produce low cost disk drives, however, necessitates a reduction in the cost of manufacturing magnetic recording disks.
Another trend in the design of disk drives is to increase the recording density of a disk drive system. Recording density is a measure of the amount of data that may be stored in a given area of a disk. For example, to increase recording density, head technology has migrated from ferrite heads to film heads and later to magneto-resistive (MR) heads and giant magneto-resistive (GMR) heads. Another method for increasing recording densities is to pattern the surface of the disk to form discrete data tracks, referred to as discrete track recording (DTR) disks. DTR disks typically have a series of concentric raised areas (a.k.a. crests, hills, lands, elevations, etc.) storing data and recessed areas (a.k.a. troughs, valleys, grooves, etc.) that provide inter-track isolation to reduce noise. Such recessed zones may also store servo information. The recessed areas separate the raised areas to inhibit or prevent the unintended storage of data in the recessed areas.
One prior method of producing patterned magnetic recording disks is discussed in U.S. Pat. No. 6,627,254. U.S. Pat. No. 6,627,254 describes the manufacture of a disk having patterned data and CSS zones that are formed utilizing embossing techniques. The CSS zone is provided with a pattern of raised and recessed areas to reduce the stiction between the disk's surface and the flying slider. U.S. Pat. No. 6,627,254 describes two types of patterns, a checkerboard pattern and a sinusoidal pattern, both of which have a constant ratio of raised area to recessed area dimensions across the CSS zone. One problem with such a disk is the abrupt topographical change on the surface of the disk when the slider moves into the CSS zone. Abrupt topographical changes on the surface of a magnetic recording disk may affect the flying stability and glide performance of a slider and may also detrimentally affect the reliability of the slider-disk interface.